Control system of industrial truck and controlling method of the same

ABSTRACT

A control system of an industrial truck includes a first switch, a second switch and a hydraulic circuit. The first switch detects whether an operator sits down on a seat, and carries out a first operation based on the detecting result. The second switch detects whether a device for operating an actuator is operated, and carries out a second operation based on the detecting result. The hydraulic circuit is used for operating of the actuator. The hydraulic circuit includes: a control valve, a first circulating line, a hydraulic line and a drive lock valve. The control valve includes a spool that position is changed by the device. The first circulating line includes the control valve, through which the hydraulic fluid circulates. The hydraulic line connects the spool with the actuator, through which the hydraulic fluid passes. The drive lock valve is provided for the hydraulic line, and blocks the hydraulic line, based on the first operation and/or the second operation.

CROSS REFERENCE

[0001] The present invention relates to U.S. patent application Ser. No.______ entitled “CONTROL SYSTEM OF SELF PROPELLERED INDUSTRIAL MACHINE”and claiming a priority based on Japanese Patent Application No.2003-153304. The disclosures of them are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a control system of anindustrial truck and a controlling method of the same. Moreparticularly, the present invention relates to a control system of theindustrial truck and the controlling method of the same for theindustrial truck such as a fork-lift truck.

[0004] 2. Description of the Related Art

[0005] It is known that industrial trucks (vehicles), such as afork-lift and a truck crane, work to lift and moves loads by applyingtheir force as external forces directly to the loads. When theseindustrial trucks are operated, an operating condition for their machineelement is required more strictly than that of automobiles, such as apassenger motor car. The automobiles transport persons and luggage,while they do not apply their force directly to persons and luggage. Oneof the required operating conditions is a safety condition regarding asafety operation. In the passenger motor car, a wheel stoppage is theimportant safety conditions. In addition, a relation between a wheelrotation state and a machine operation state is also the importantsafety conditions in the industrial truck.

[0006] In conjunction with the above description, Japanese Laid OpenPatent Application (JP-A-Heisei 07-76498) discloses the followingindustrial truck. In this industrial truck, the safety is secured byconsidering a positioning relation between the industrial truck body andits operator (driver). The industrial truck includes a seat switch thatoutputs the seating signal corresponding to the seating of the operatoron the seat of the body. The existence of the seating signal outputtedby the seat switch is one element of a machine operation enablingcondition. The non-existence of the seating signal (including thenon-existence of the delayed seating signal) in one element of a machineoperation disabling condition. This industrial truck achieves both ofhigh safety and operationality.

[0007] The non-seating signal, which is outputted when the operator doesnot sit on a seat, can be effectively utilized.

[0008] It is effective to prepare a control valve for controlling ahydraulic pressure distribution of the work machine in order to prohibitor limit the machine operation corresponding to the non-seating signal.The industrial truck with such the control valve disclosed in theJapanese Laid Open Patent Application S64-60598, S64-60599 and the U.S.Pat. No. 5,577,876.

[0009] When outputting the non-seating signal, preventing hydraulic oilin the hydraulic pressure cylinder from returning by a mechanicalcontrol of the control valve should be important to secure desiredsafety. It is desired for simplifying a hydraulic circuit to takeadvantage of the conventional mechanical controlling function of thecontrol valve.

[0010] The followings are the Japanese Laid Open Patent Applications andthe U.S. Patent as described above.

[0011] A control method of a control valve for landing and loading forvehicle is disclosed in the Japanese Laid Open Patent ApplicationS64-60598. In this control method, the vehicle is controlled bypreparing an switch valve in either of a pilot hydraulic oil pipe routeand two pilot drain pipe routes, or in both of them. The control valvefor landing and loading in the vehicle is controlled at the hydraulicpressure control circuit. Here, the pilot hydraulic oil pipe routeprovides pilot hydraulic oil to the spool of the control valve whichcontrols a decompression actuator. The pilot drain pipe route isprepared in response to the pilot hydraulic oil pipe route and is usedfor providing the pilot hydraulic oil. The switch valve is opened andclosed by an electric signal which is outputted from the controlapparatus on the basis of an operation signal, a seating signal and anauxiliary operation signal. The operation signal corresponds to theoperation of means of landing and loading operation. The seating signaldetects that the operator sits the seat and is outputted from the seatswitch. The auxiliary operation signal is outputted from an auxiliaryswitch which the operator can use arbitrarily when he does not seat. Thecontrol valve for landing and loading in the vehicle is controlled bythis control method as follow. When the seating signal or the auxiliaryoperation signal are inputted to the control apparatus continuously fora predetermined time, a control signal which corresponds to theoperation of the means of landing and loading operation is outputted tothe switch valve. When the means of landing and loading operation isoperated before the seating signal or the auxiliary operation signal isinputted to the control apparatus, or when the seating signal or theauxiliary operation signal is inputted to the control apparatus duringthe operation and the input continues for a predetermined time, thecontrol signal in low level is outputted to the switch valve at thefirst, and the level of the control signal is gradually raised inaccordance with a present volume of the operation of the means oflanding and loading.

[0012] Further, a control method of a control valve for landing andloading for vehicle is also disclosed in the Japanese Laid Open PatentApplication S64-60599 as the related technique. In this control method,the vehicle is controlled by preparing an switch valve in either of apilot hydraulic oil pipe route and two pilot drain pipe routes, or inboth of them. The control valve for landing and loading in the vehicleis controlled at the hydraulic pressure control circuit. Here, the pilothydraulic oil pipe route provides pilot hydraulic oil to the spool ofthe control valve which controls a decompression actuator. The pilotdrain pipe route is prepared in response to the pilot hydraulic oil piperoute and is used for providing the pilot hydraulic oil. The switchvalve is opened and closed by an electric signal which is outputted fromthe control apparatus on the basis of an operation signal, a seatingsignal and an auxiliary operation signal. The operation signalcorresponds to the operation of means of landing and loading operation.The seating signal detects that the operator sits the seat and isoutputted from the seat switch. The auxiliary operation signal isoutputted from an auxiliary switch which the operator can usearbitrarily when he does not seat. The control valve for landing andloading in the vehicle is controlled by this control method as follow.When the seating signal from the seat switch or the auxiliary operationsignal from the auxiliary switch are inputted to the control apparatus,a control signal which corresponds to the operation of the means oflanding and loading operation is outputted to the switch valve. When themeans of landing and loading operation is operated before the seatingsignal from the seating switch or the auxiliary operation signal fromthe auxiliary switch is inputted to the control apparatus, or when theseating signal or the auxiliary operation signal is inputted to thecontrol apparatus during the operation, the control signal in low levelis outputted to the switch valve at the first, and the level of thecontrol signal is gradually raised in accordance with a present volumeof the operation of the means of landing and loading.

[0013] Further, a control apparatus of a fork-lift is disclosed in theJapanese Laid Open Patent Application H7-76498 as the related technique.The fork-lift includes a seating switch which is switched ON and OFFaccording to the seating or non-seating of the operator. The controlapparatus determines permission or a prohibition of the operation of themachine for loading and landing works on the basis of the ON/OFF stateof this seating switch. The operation for the works is possible to bepermitted immediately when the seat switch switches to either state ofON and OFF by operator's seating. On the other hand, being switched tothe other by an operator's standing and continued this state for apredetermined time, the operation for the works is prohibited.

[0014] Furthermore In conjunction with the above description, U.S. Pat.No. 5,577,876 discloses the following technique. In a skid steer loaderof the type having a control apparatus for controlling movement of alift arm on the skid steer loader, the improvement includes: poweractuator means; a hydraulic power circuit; a sensor; power interruptionmeans; and manually operable bypass means. The power actuator means iscoupled to the lift arm, for moving the lift arm along a path. Thehydraulic power circuit is coupled to the power actuator means,providing hydraulic power to the power actuator means, along a firstpower path, to move the lift arm in a first direction. The sensor iscoupled to the skid steer loader, for sensing a desired parameter andproviding a sensor signal indicative of the desired parameter. The powerinterruption means includes a first hydraulic valve coupled in the firstpower path to the power actuator means and the sensor, for interruptingpower to the power actuator means based on the sensor signal. Themanually operable bypass means includes a second hydraulic valve coupledto the hydraulic power circuit and the power actuator means, forproviding a second power path between the hydraulic power circuit andthe power actuator means, bypassing the power interruption means toallow movement of the lift arm.

SUMMARY OF THE INVENTION

[0015] Therefore, an object of the present invention is to provide acontrol system of an industrial truck that can prevent hydraulic oil inthe hydraulic pressure cylinder from returning by a mechanical controlof the control valve to secure desired safety, and a controlling methodof the same.

[0016] Another object of the present invention is to provide a controlsystem of an industrial truck that can hold simplicity of a hydrauliccircuit having the advantage of the conventional mechanical controllingfunction of the control valve to achieve the above object, and acontrolling method of the same.

[0017] These and other objects, features and advantages of the presentinvention will be readily ascertained by referring to the followingdescription and drawings.

[0018] In order to achieve an aspect of the present invention, thepresent invention provides a control system of an industrial truckincluding: a first switch, a second switch and a hydraulic circuit. Thefirst switch is provided for a (vehicle) body. The first switch detectswhether or not an operator sits down on a seat, and carries out a firstoperation based on the detecting result by the first switch. The secondswitch is provided for the main body. The second switch detects whetheror not a device for operating an actuator is operated, and carries out asecond operation based on the detecting result by the second switch. Thehydraulic circuit is used for operating of the actuator and containshydraulic fluid. The hydraulic circuit includes: a control valve, afirst circulating line, a hydraulic line and a drive lock valve. Thecontrol valve includes a spool that position is changed by the device.The first circulating line includes the control valve. The hydraulicfluid circulates through the first circulating line. The hydraulic lineconnects the spool with the actuator, wherein the hydraulic fluid passesthrough the hydraulic line. The drive lock valve is provided for thehydraulic line. The drive lock valve blocks the hydraulic line, based onone of the first operation and the first and second operations.

[0019] In the control system of an industrial truck according to thepresent invention, the drive lock valve blocks the hydraulic line byclosing the drive lock valve, under a condition that the first switchdoes not carries out the first operation.

[0020] In the control system of an industrial truck according to thepresent invention, the first operation is to output a first signalindicating that the operator sits down on the seat. The second operationis to output a second signal indicating that the device for operating anactuator is operated.

[0021] In the control system of an industrial truck according to thepresent invention, the first operation is carried out when apredetermined time period passes since just after a first status changesto a second status. The first status indicates that the first switch isdetecting that the operator sits down on the seat. The second statusindicates that the first switch is detecting that the operator does notsit down on the seat.

[0022] In the control system of an industrial truck according to thepresent invention, the hydraulic circuit further includes: a secondcirculating line and an unloading valve. The second circulating line isconnected in parallel with the first circulating line, and does notinclude the control valve. The hydraulic fluid bypasses the controlvalve through second circulating line. The unloading valve operates inresponse to the first operation, and is included in the secondcirculating line. The unloading valve is opened to connect an upstreamof the unloading valve with a hydraulic fluid tank directly, based onone of the first operation and the first and second operations.

[0023] In the control system of an industrial truck according to thepresent invention, the unloading valve is opened to connect an upstreamof the unloading valve with the hydraulic fluid tank directly, under acondition that the first switch does not carries out the firstoperation.

[0024] The control system of an industrial truck according to thepresent invention, further including: a controller which controls thedrive lock valve and the unloading valve based on the one of the firstoperation and the first and second operations.

[0025] In the control system of an industrial truck according to thepresent invention, the second switch outputs electric signalcorresponding to operational positions of the device.

[0026] In the control system of an industrial truck according to thepresent invention, the actuator is operated for a certain direction byusing the gravitation against a machine element.

[0027] In the control system of an industrial truck according to thepresent invention, the machine element is one of a crane arm of a truckcrane, a shovel of a shovel type excavator, a fork of a fork-lift truck,a ladder of a fire-fighting vehicle, a hatch of a refuse collector and aramp of a car carrier.

[0028] In order to achieve another aspect of the present invention, thepresent invention provides a controlling method of an industrial truck.Here, the industrial truck including: a first switch which is providedfor a (vehicle) body; a second switch which is provided for the body;and a hydraulic circuit which is used for operating of the actuator andincludes hydraulic fluid. The hydraulic circuit includes: a controlvalve, a first circulating line, a hydraulic line and a drive lockvalve. The control valve includes a spool that position is changed bythe operating device. The first circulating line includes the controlvalve, wherein the hydraulic fluid circulates through the firstcirculating line. The hydraulic line connects the spool with theactuator, wherein the hydraulic fluid passes through the hydraulic line.The drive lock valve which is provided for the hydraulic line. Thecontrolling method including: (a) detecting whether or not an operatorsits down on a seat, and carrying out a first operation based on thedetection result by the first switch; (b) detecting whether or not adevice for operating an actuator is operated, and carrying out a secondoperation based on the detection result by the second switch; and (c)carrying out blocks the hydraulic line by using the drive lock valve,based on one of the first operation and the first and second operations.

[0029] In the controlling method of an industrial truck according to thepresent invention, the step (c) includes: (c1) closing the drive lockvalve to block the hydraulic line under a condition that the firstswitch does not carries out the first operation.

[0030] In the controlling method of an industrial truck according to thepresent invention, the first operation is to output a first signalindicating that the operator sits down on the seat. The second operationis to output a second signal indicating that the device for operating anactuator is operated.

[0031] In the controlling method of an industrial truck according to thepresent invention, the step (a) includes: (a1) detecting a first statusthat the operator sits down on the seat; (a2) detecting a second statusthat the operator does not sit down on the seat; and (a3) carrying outthe first operation when a predetermined time period passes since justafter the first situation changes to the second situation.

[0032] In the controlling method of an industrial truck according to thepresent invention, the first operation takes priority of the secondoperation in the step (c).

[0033] In the controlling method of an industrial truck according to thepresent invention, the actuator is operated for a certain direction byusing the gravitation against a machine element.

[0034] In the controlling method of an industrial truck according to thepresent invention, the step (b) includes: (b1) detecting whether or nota device for operating an actuator is operated to a predetermineddirection, and (b2) carrying out a second operation when the device isoperated to the predetermined direction.

[0035] The controlling method of an industrial truck according to thepresent invention, further including: (d) opening a unloading valve toconnect an upstream of the unloading valve with an hydraulic fluid tankdirectly, based on one of the first operation and the first and secondoperations. The unloading valve is included in a second circulatingline, and operates in response to the first operation. The secondcirculating line is connected in parallel with the first circulatingline, and does not include the control valve, wherein the hydraulicfluid bypasses the control valve through second circulating line.

[0036] In the controlling method of an industrial truck according to thepresent invention, the step (d) includes: (d1) opening the unloadingvalve to connect said upstream of the unloading valve with the hydraulicfluid tank directly, under a condition that the first switch does notcarries out the first operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a schematic view showing a fork-lift truck as anindustrial truck to which the control system of the present invention isapplied;

[0038]FIG. 2 is a schematic view showing the forward and reverse handlelever;

[0039]FIG. 3 is a schematic view showing a hydraulic circuit to drive aplurality of working components for the fork lift;

[0040]FIG. 4 is a schematic view showing the manual handle lever;

[0041]FIG. 5 is a schematic view showing an end portion of the forwardand backward link;

[0042]FIG. 6 is a schematic view showing the direction detecting switch;

[0043]FIG. 7 is a schematic block diagram showing logic of thecontroller;

[0044]FIG. 8 is a flowchart showing a method for generating the seatingsignal; and

[0045]FIG. 9 is a flowchart showing the operation of the embodiment ofthe controlling method of the industrial truck according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Embodiments of a control system of an industrial truck and acontrolling method of the same according to the present invention willbe described below with reference to the attached drawings.

[0047] Firstly, the configuration of the embodiment of the controlsystem of the industrial truck according to the present invention willbe described.

[0048]FIG. 1 is a schematic view showing a fork-lift truck as anindustrial truck to which the control system of the present invention isapplied.

[0049] The main body 1 of the fork-lift truck (industrial truck) isprovided with a machine element (5) and a seat 4. The main body 1 runson the ground surface 3 such as a road surface (including an off-roadsurface) with wheel 2. Wheel 2 can run on the ground surface 3 withcaterpillar track.

[0050] Here, other examples of the industrial trucks are a truck crane,a shovel type excavator, a fire-fighting vehicle, a refuse collector anda car carrier. The machine element of these industrial trucks are acrane arm of the truck crane, a shovel of the shovel type excavator, aladder of the fire-fighting vehicle, a hatch of the refuse collector anda ramp of the car carrier. However, the present invention is not limitedto these examples.

[0051] The seat 4 is arranged to the proper portion of the main body 1.A driver or an operator sits on the seat 4. The main body 1 is equippedwith the fork lift 5 as the work machine. The fork lift 5 is composed ofan outer mast 6, an inner mast 7 and a fork 8. The inner mast 7 islifted up and down to the vertical direction guided by the outer mast 6.The fork 8 is lifted up and down supported by the inner mast 7 in anintegrated manner to the inner mast 7. The inner mast 7 is driven tolift up and down by a lift cylinder 9.

[0052] A forward and reverse handle lever 11 is arranged in front of theseat 4. The forward and reverse handle lever 11 is supported to berotatable against the main body 1. FIG. 2 is a schematic view showingthe forward and reverse handle lever 11. The forward and reverse handlelever 11 rotates around an axis of rotation 12 with reciprocatingmotion. The axis of rotation has a vertical direction or the inclineddirection against the vertical direction. A clockwise rotation of theforward and reverse handle lever 11 corresponds to a forward position Fcorresponding to forward movement of the main body 1. A counterclockwiserotation of the forward and reverse handle lever 11 corresponds to areverse position R corresponding to reverse movement of the main body 1.The forward and reverse handle lever 11 can be stayed stably at theposition of a neutral position N.

[0053] A foot stand 13 is arranged in front and lower position of theseat 4 in the main body 1. Sitting on the seat 4, the operator puts hislegs on the foot stand 13. The operator can stand on the foot stand 13when standing up from the seat 4. The operator getting on and off themain body 1 might accidentally touch other driving apparatus for themachine element which is arranged around the forward and reverse handlelever 11 or the foot stand 13.

[0054]FIG. 3 is a schematic view showing a hydraulic circuit 14 to drivea plurality of working components for the fork lift 5. The main body 1is equipped with a hydraulic circuit 14 and a hydraulic oil circulatingcircuit 16 including a pump 15. The pump 15, an oil tank 17 and controlvalves 18 are connected with each other through a hydraulic oilcirculation pipes (lines) which are included in the hydraulic oilcirculating circuit 16. The pump 15 is mathematically coupled to anengine 19. The engine 19 as a motor is not an electric motor but is aninternal combustion engine (for example, a gasoline engine, a dieselengine, a hybrid engine combined to an electric motor). The hydrauliccircuit 14 includes a steering valve circuit 21 which connects inparallel to the hydraulic oil circulating circuit 16.

[0055] The control valves 18 are composed of a first control valve 22, asecond control valve 23 and a third control valve 24. The first controlvalve 22 selectively forms the first hydraulic oil route switchingcircuit which switches (changes) the lift up and down of the liftcylinder 9. The second control valve 23 selectively forms the secondhydraulic oil route switching circuit which switches a tilt position ofa tilt cylinder 25. The tilt position can be switched (changed)continuously. The third control valve 24 selectively forms the thirdhydraulic oil route switching circuit that switches a drive state ofanother drive portion (not shown). The tilt cylinder 25 can adjust anangle of the outer mast 6 to the vertical surface. The fourth controlvalve 26 can selectively distribute the hydraulic oil to the hydrauliccircuit 14 and the steering valve circuit 21.

[0056] The first control valve 22 includes a three-position selectionvalve. The three-position selection valve includes a spool which isselectively positioned in one of three positions. The three positionscorresponds to the three route of the first hydraulic oil routeswitching circuit. In FIG. 3, the spool is positioned in the neutralposition among the three positions. The hydraulic oil is pumped out ofthe oil tank 17 by the pump 15. It is distributed to the control valves18 by the fourth control valve 26. It is refluxed to the oil tank 17through a reflux line 27 that is a part of the hydraulic oil circulatingcircuit 16. The reflux line 27 is composed of the neutral position 22Nof the first control valve 22, a neutral position 23N of the secondcontrol valve 23 and a neutral position 24N of the third control valves24.

[0057] A three-direction distributor 28 is provided in an upstream partto the first control valve 22 in the hydraulic oil circulating circuit16, between the fourth control valve 26 and the first control valve 22.The three-direction distributor 28 can simultaneously supply pressuredhydraulic oil to each of the first hydraulic oil supplying port 29 ofthe first control valves 22, the second hydraulic oil supplying port 31of the second control valves 23 and the third hydraulic oil supplyingport 32 of the third control valves 24. A two-direction reflux gatherer33 is provided in a downstream part to the third control valve 24 in thehydraulic oil circulating circuit 16, between the third control valve 24and the oil tank 17. The three-direction distributor 28 connects withthe two-direction reflux gatherer 33 through a reflux route line 34. Thethree-direction distributor 28 connects with each of the secondhydraulic oil supplying port 31 and the third hydraulic oil supplyingport 32 through each of nodes 35 and 36 in the reflux route line 34,respectively. The connection does not make any resistance of thehydraulic oil, except for unintended resistance such as a pipingresistance is ignored). A first check valve 37 is provided between thethree-direction distributor 28 and the first hydraulic oil supplyingport 29. A second check valve 38 is provided between the node 35 and thesecond hydraulic oil supplying port 31. A third check valve 39 isprovided between the node 36 and the third hydraulic oil supplying port32.

[0058] An unloading valve 41 is provided in a downstream part to thenode 36 in the reflux route line 34, between the node 36 and thetwo-direction reflux gatherer 33. If an unloading signal, that will bedescribed later, is not supplyed to the unloading valve 41, theunloading valve 41 releases the reflux route line 34, and thethree-direction distributor 28 connects with the two-direction refluxgatherer 33 without resistance.

[0059] Switching the three positions of the first control valve 22 isoperated by a manual handle lever 42. FIG. 4 is a schematic view showingthe manual handle lever 42. The manual handle lever 42 is provided asone of a plurality of manual handle levers. The manual handle lever 42is composed of an inclining handle lever 43, an inclining supportelement 44, a movement converter 45, a forward and backward link 46. Theinclining handle lever 43 is operated with inclined movement by theoperator's fingers. The inclining support element 44 supports theinclining handle lever 43 to be inclined freely. The movement converter45 converts the inclining movement of the inclining handle lever 43 intothe rectilinear movement. The forward and backward link 46 movesrectilinearly corresponding to the inclined movement of the inclininghandle lever 43 converted by the movement converter 45. The forward andbackward movement of the forward and backward link 46 corresponds to thechange among the three positions of the first control valve 22 as shownin FIG. 3.

[0060] The manual handle lever 42 has another important function inaddition to such the valve operation function. FIG. 5 is a schematicview showing an end portion of the forward and backward link 46. Adirection detecting switch 47 is fixed to the main body (fixed portion)of the first control valve 22 (not shown in this figure) near the endportion of the forward and backward link 46. The direction detectingswitch 47 detects a direction of the movement of the manual handle lever42.

[0061]FIG. 6 is a schematic view showing the direction detecting switch47. The direction detecting switch 47 is composed of a switch box 48, aswitch lever 49 and a contact type switch button 51. The switch lever 49is supported by the case of the switch box 48 with axis pin and can beinclined freely. The forward and backward link 46 has a slope 52 that isits peripheral area. A roller 53 is fixed on a freely inclining end ofswitch lever 49, which can rotate freely. The roller 53 rolls on theslope 52 when the forward and backward link 46 moves forward andbackward. When the inclining handle lever 43 is pulled (to the driverdirection) and the forward and backward link 46 moves forward to themovement direction (downward in the vertical direction), the switchlever 49 is inclined together with the roller 53 rolling on the slope52. The contact type switch button 51 is inserted into the switch box 48to turn on an electric contact type switch in the switch box 48. In thisway, the manual handle lever 42 can detect a lifting down operation andgenerate a lifting down order signal (an operation start signal:described later) that indicates an order to drive pistons (not shown indrawings) of the lift cylinder 9 to the lift down direction. Theswitching operations of the other manual handle levers 54 and 55 (referto FIG. 3 and FIG. 4) are the same as that of the manual handle lever42. The manual handle lever 54 can generate a signal (another operationstart signal) to drive the tilt cylinder 25. The manual handle lever 55can generate a signal (still another operation start signal) to drivethe another actuator.

[0062] The control system of the industrial truck according to thepresent invention includes a lift lock valve 56 as shown in FIG. 3. Thelift lock valve 56 is provided between the lift cylinder 9 and a liftingdown direction portion 22D of the first control valve 22. The liftingdown direction portion 22D is moved to the movement position (a positionwhere the neutral portion 22N is set in FIG. 3) by the lifting downoperation of the manual handle lever 42. The lift lock valve 56 isprovided as a pocket valve that opens or closes corresponding to abinary lock signal. That is, it is composed of a lock operation valve 57and an switch valve 58. The lock operation valve 57 is changed to twopositions corresponding to the binary lock signal. The switch valve 58is opened or closed corresponding to the changing position of the lockoperation valve 57. The binary signal (an drive lock signal: describedlater) is generated and outputted by a controller 61 (described later)based on the operation start signal 59 (referring to FIG. 7). Theoperation start signal 59 is generated by the direction detecting switch47 corresponding to moving in and out of the contact type switch button51 which corresponds to the two inclining position of the switch lever49. The operation start signal 59 is concretely generated as the mastlifting down signal or the fork lifting down signal.

[0063]FIG. 7 is a schematic block diagram showing logic of thecontroller 61. The controller 61 includes a seat delay counter 73 thatcounts the seconds by using its built-in clock. In FIG. 7, an unloadingsignal generating process 64 a and a drive lock signal generatingprocess 65 a are clearly indicated, which are the processes that thecontroller 61 executes. The controller 61 includes the means whichexecutes these processes (not shown). A logic circuit 62 including aseat switch 62 a and the direction detecting switch 47 is connected withthe controller 61. The Logic circuit 62 is embedded in the seat 4. Here,the logic circuit 62 (the seating switch 62 a) senses (detects) theweight of the operator sitting on (riding on and boarding on) the mainbody 1 so as to output a operator boarding signal (the seating signal)63. The seating signal 63 is generated by the seat switch 62 a (forexample, a plane-type contact switch (not shown)), which is pushed downby the weight of the operator's body sitting on the seat 4. Thedirection detecting switch 47 outputs the operation start signal 59based on the motion of the manual handle lever 42 as mentioned above.The operation start signal 59 is supplied to the controller 61 togetherwith the seating signal 63. The controller 61 executes the unloadingsignal generating process 64 a and generates the unloading signal 64 bya logic process described later, based on the operation start signal 59and the seating signal 63. The unloading signal 64 drives the unloadingvalve 41. The unloading signal 64 is outputted through a signal line toan unloading solenoid 68 to drive the unloading valve 41. The controller61 executes the drive lock signal generating process 65 a and generatesthe drive lock signal 65 by the logic process described later, based onthe operation start signal 59 and the seating signal 63. The drive locksignal 65 drives the lift lock valve 56. The drive lock signal 65 isoutputted through a signal line to a drive lock solenoid 69 to drive thelift lock valve 56. Also, the controller 61 outputs a mast lock alarmsignal 71 to an alarm 72 by the logic process which is also describedlater, based on the operation start signal 59 and the seating signal 63.

[0064]FIG. 8 is a flowchart showing a method for generating the seatingsignal 63 (The judgement of the operator's seating). When the operatorsits on the seat 4, the seat switch 62 a is turned on and the seatingsignal 63 is outputted.

[0065] In the step S1, the controller 61 judges whether or not the seatswitch 62 a is ON. When judging that the seat switch 62 a is ON (judgingthat the operator is sitting, step S1: YES), the controller 61 resetsthe seat delay counter 73 to zero in the Step S2. Then, the controller61 sets a seating flag in the Step 3.

[0066] When judging that the seat switch 62 a is not ON (judging thatthe operator is not sitting, step S1: NO), the controller 61 starts tomake the seat delay counter 73 count time in the Step S4. When the timeperiod counted by the seat delay counter 73 is equal to or less than thepredetermined time (the predetermined time has not passed during thenon-seating time, step S5: NO) in the Step S5, the controller 61 setsthe seating flag (maintains a setting state) in the step S3, asmentioned above. When the time period counted by the seat delay counter73 is more than the predetermined time (the predetermined time haspassed during the non-seating time, step S5: YES) in the Step S5, thecontroller 61 resets the seating flag in the Step S6. Theabove-mentioned predetermined time is preferably 1.5 seconds as anempirical rule. In this way, when the sitting operator stands up or getsoff the main body 1, the controller 61 resets the seating flag after 1.5seconds pass from the standing up or the getting off time. It is judgedwhether or not the operator is sitting by controlling the seating flag.

[0067] In FIG. 8, before standing up, the operator is sitting on theseat 4 in the operation allowing state that the drive of the actuator ispermissible. During the time within 1.5 seconds after the operatorstands up from the seat 4, the seating flag is set and the operation ofthe actuator can not be prohibited based on the setting of the seatingflag. Here, the descent of the mast is essentially important as theoperation of the actuator. When noticing the something unusual in thestate of the load, the operator might get off or jump off the fork-lifttruck and approach the fork. Using the seating flag, the operator canefficiently prevent from the attack by the fork. It is effective thatthe time from getting off the fork-lift truck to approach the forkshould be set in 1.5 seconds as an empirical rule. It is also effectivethat the time from standing up on the seat 4 to checking the fork andthe load on the seat 4 should be set in 1.5 seconds as an empiricalrule.

[0068] The logic circuit 62 outputs an electrically low state signal(ex. 0V signal) corresponding to the ON state of the seat switch 62 a.On the other hand, the logic circuit 62 outputs an electrically highstate signal (ex. 5V signal) corresponding to the OFF state of the seatswitch 62 a. Therefore, if the electric system of the logic circuit 62is out of order, the logic circuit 62 outputs 0V signal so that thecontroller 61 outputs to output the OFF state signal.

[0069] Next, the operation of the embodiment of the controlling methodof the industrial truck according to the present invention will bedescribed.

[0070] A forward inclination of the manual handle lever 42 correspondsto a raising operation of the mast. By the forward inclination of themanual handle lever 42, the spool of the first control valve 22 at thestate position of FIG. 3 (the neutral portion 22N) moves (displaces) tothe right (lift up direction) position in FIG. 3. The lift up directionportion 22U in the spool of the first control valve 22 is set to theoperating position. The hydraulic oil of the hydraulic oil circulatingcircuit 16 passes through the fourth control valve 26, branches at thethree-direction distributor 28. Then, the hydraulic oil passes throughthe first check valve 37 and a line 74 in the right position of the liftup direction portion 22U. The switch valve 58 is opened by the pressureof the hydraulic oil of a hydraulic oil supply line 75 which connectswith an output port of the first control valve 22. The hydraulic oilpassing through the line 74 is supplied to the each of the supply sideof the two lift cylinders 9 through a lift cylinder operation line 76.By this supplying the hydraulic oil, pistons 77 of the lift cylinders 9are raised and the inner masts 7 are pushed up to the upper verticaldirection together with the pistons 77. A part of free oil at the sideof the discharge of the lift cylinders 9 is refluxed to the oil tank 17through a return line 78

[0071] A backward inclination of the manual handle lever 42 (pulling thelever) corresponds to a lifting down operation of the mast. By thebackward inclination of the manual handle lever 42, the spool of thefirst control valve 22 at the state position of FIG. 3 (the neutralportion 22N) moves (displaces) to the left (lift down direction)position in FIG. 3. The lift down direction portion 22D in the spool ofthe first control valve 22 is set to the operating position. Thehydraulic oil of the hydraulic oil circulating circuit 16 passes throughthe fourth control valve 26, branches at the three-direction distributor28. A first line 79 of the lifting down direction portion 22D makes thehydraulic oil from the three-direction distributor 2 pass through. Thehydraulic oil is supplied to the second control valve 23, which controlsthe motion of the other actuator (the tilt cylinder 25). A second line81 of the lifting down direction portion 22D connects the switch valve58 and a reflux line 83. An operation start signal 59 is outputted fromthe direction detecting switch 47 by the lifting down operation (thelifting down operation and pulling the lever). The controller 61 outputsthe drive lock signal 65 corresponding to the operation start signal 59to the drive lock solenoid 69. This causes that the lift lock valve 56is ON and the switch valve 58 is opened. If the manual handle lever 42is operated so that the switch valve 58 is opened, the hydraulic oil ofthe lift cylinder 9, which receives the weight of the inner mast 7 onthe supply side of the lift cylinder 9, passes through the second line81 and the reflux line 83 to the oil tank 17. As a result, the innermast 7 can be lifted down.

[0072] The operation start signal 59 is an electrically high statesignal (ex. 5V signal) corresponding to the OFF state, when there is nopulling operation of the manual handle lever 42, that is the similar tothe seating signal 63.

[0073]FIG. 9 is a flowchart showing the operation of the embodiment ofthe controlling method of the industrial truck according to the presentinvention. A safety measure by setting of the above-mentioned seatingflag is incorporated into this embodiment. The embodiment is mainlydescribed below as a mast lock control, especially the lifting downoperation of the manual handle lever 42.

[0074] In the step S11 in FIG. 9, if the direction detecting switch 47of the manual handle lever 42 is not ON (step S11: NO), that is thestate of no pulling, the mast lock (lift) flag is reset (the OFF state)in the step S12. Here, the mast lock (lift) flag is initialized to bethe ON state at the starting.

[0075] If the direction detecting switch 47 is ON (step S11: YES), thatis the state of pulling, the mast lock (lift) flag is in the same stateas before.

[0076] In the Step S13, if the direction detecting switch 47 of themanual handle lever 54 is not ON (step S13: NO), the mast lock (tilt)flag is reset (the OFF state) in the step S14. Here, the mast lock(tilt) flag is also initialized to be the ON state at the starting.

[0077] If the direction detecting switch 47 is ON (step S13: YES), themast lock (tilt) flag is in the same state as before.

[0078] The state of another lock flag of the direction detecting switch47 of the manual handle lever 55 for other actuator may be checked bythe same process as steps S11 to S12.

[0079] When operation is started, the steps S12 and S14 should beprocessed. Therefore, a plurality of lock flags are reset (the OFFstate) under the AND condition.

[0080] If the seating flag is set (in the ON state) as described in FIG.8 in the step S15 (YES), and both of the mast lock (lift, tilt) flags isin the OFF state in the step S16 (YES), the process goes to the stepS17. When operation is started, as both of the mast lock flag is in OFFstate in the steps S12 and S14, the process goes to the step S17.

[0081] In the step S17, the unloading solenoid 68 is operated to shutthe unloading valve 41. Therefore, the control valves 18 becomes to be anon-conductive state. In this condition, the actuators are possible tomove. A mast lock alert lamp turns off that indicates all of the mastlocks are released in the step S18.

[0082] In this case, if the manual handle lever 42 moves (pullingoperation) and the direction detecting switch 47 is ON, YES is selectedin the step S19. The drive lock solenoid 69 is moved in response to thedrive lock signal 65 so as not to move the lock operation valve 57, thenthe switch valve 58 is opened in the step S20. In this way, the liftlock valve 56 is in the ON state and the lifting down lock is unlocked(released).

[0083] On the other hand, if the manual handle lever 42 does not move(no pulling operation) and the direction detecting switch 47 is OFF, NOis selected in the step S19. The drive lock solenoid 69 is moved inresponse to the drive lock signal 65 so as to move the lock operationvalve 57, then the switch valve 58 is closed in the step S21. In thisway, the lift lock valve 56 is in the OFF state and the lifting downlock is locked.

[0084] When the manual handle lever 42 is not operated (no pullingoperation) so that the switch valve 58 is closed, the hydraulic oil ofthe lift cylinder 9, which receives the weight of the inner mast 7 onthe supply side of the lift cylinder 9, is blocked off by the switchvalve 58 and the inner mast 7 does not lift down.

[0085] On the other hand, if the manual handle lever 42 is operated(pulling operation) so that the switch valve 58 is opened, the hydraulicoil of the lift cylinder 9 is not blocked off by the switch valve 58.The hydraulic oil passes to the oil tank 17 through the second line 81of the lifting down direction 22D and the reflux line 83 connecting thesecond line 81 with the two-direction reflux gatherer 33. As a result,the inner mast 7 can be lifted down.

[0086] The control process turns to the step S22, if the seating flag isin the OFF state or 1.5 seconds has not passed from the seating in thestep S15 (step S15: NO). Also, the control process turns to the stepS22, if the seating flag is in the ON state in the step S15 (step S15:YES) and concurrently at least one of the manual handle levers 42 and 54is operated (the direction detecting switch 47 is ON) so that the mastlock (lift, tilt) flag is not in the OFF state in the step S16 (stepS16: NO).

[0087] In the step S22, the unloading solenoid 68 does not move and theunloading valve 41 is opened. Therefore, the hydraulic oil can passthrough the reflux route line 34 to the two-direction reflux gatherer33. In this condition, the actuators are impossible to move. The mastlock alert signal 71 corresponding to this state is outputted. The mastlock alert lamp turns on in response to the mast lock alert signal 71 inthe step S23.

[0088] In the steps S24 and S26 of the alert state, if at least one ofthe lifting down operation of the manual handle lever 42 and the tiltingoperation of the manual handle lever 54 (and the other operation of theother actuator) is carried out, the mast lock (lift) flag and the mustlock (tilt) flag (and the other actuator lock flag) are set. Then, theprocess returns to the step S11. If there is not such operations, theprocess returns to Step S11 without any change of the states of the lockflags.

[0089] When the operator does not sit on the seat 4, the unloading valve41 is opened (Step S22), and the hydraulic oil of the discharge side inthe hydraulic oil circulating circuit 16 refluxes to the oil tank 17through the reflux route line 34. Here, the operation of the manualhandle lever 42 does not give a driving force to the lift cylinder 9.

[0090] When there is the lifting down operation in the step S11, theoperator sits on the seat 4 in the step S15 and the mast lock flag inthe initial state is in the ON state, the process goes to the step S22.The operation by the operator does not give a driving force to the liftcylinder 9.

[0091] When the mast lock flag is set in the ON state in the step S25,there is the lifting down operation in the step S11 and the operatorsits on the seat 4 in the step S15, the process goes to the step S22.The operation by the operator does not give a driving force to the liftcylinder 9.

[0092] Therefore, only after all the must lock flags are reset in theOFF state, the lift cylinder 9 can be operated (moved).

[0093] According to the present invention, the safety of the mechanicalcontrol can be strengthened by adding an electric signal logic.

What is claimed is:
 1. A control system of an industrial truckcomprising: a first switch which is provided for a body, wherein saidfirst switch detects whether or not an operator sits down on a seat, andcarries out a first operation based on said detecting result by saidfirst switch; a second switch which is provided for said body, whereinsaid second switch detects whether or not a device for operating anactuator is operated, and carries out a second operation based on saiddetecting result by said second switch; and a hydraulic circuit which isused for operating of said actuator and contains hydraulic fluid,wherein said hydraulic circuit includes: a control valve which includesa spool (22D, 22N, 22U) that position is changed by said device, a firstcirculating line which includes said control valve, wherein saidhydraulic fluid circulates through said first circulating line, ahydraulic line which connects said spool (22D, 22N, 22U) with saidactuator, wherein said hydraulic fluid passes through said hydraulicline, and a drive lock valve which is provided for said hydraulic line,said drive lock valve blocks said hydraulic line, based on one of saidfirst operation and said first and second operations.
 2. The controlsystem of an industrial truck according to claim 1, wherein said drivelock valve blocks said hydraulic line by closing said drive lock valveunder a condition that said first switch does not carries out said firstoperation.
 3. The control system of an industrial truck according toclaim 1, wherein said first operation is to output a first signalindicating that said operator sits down on the seat, and said secondoperation is to output a second signal indicating that said device foroperating an actuator is operated.
 4. The control system of anindustrial truck according to claim 1, wherein said first operation iscarried out when a predetermined time period passes since just after afirst status changes to a second status, said first status indicatesthat said first switch is detecting that said operator sits down on theseat, and said second status indicates that said first switch isdetecting that said operator does not sit down on the seat.
 5. Thecontrol system of an industrial truck according to claim 1, wherein saidhydraulic circuit further includes: a second circulating line which isconnected in parallel with said first circulating line, and does notinclude said control valve, wherein said hydraulic fluid bypasses saidcontrol valve through second circulating line, and an unloading valvewhich operates in response to said first operation, and is included insaid second circulating line, said unloading valve is opened to connectan upstream of said unloading valve with an hydraulic fluid tankdirectly, based on one of said first operation and said first and secondoperations.
 6. The control system of an industrial truck according to 5,wherein said unloading valve is opened to connect an upstream of saidunloading valve with said hydraulic fluid tank directly, under acondition that said first switch does not carries out said firstoperation.
 7. The control system of an industrial truck according toclaim 5, further comprising: a controller which controls said drive lockvalve and said unloading valve based on said one of said first operationand said first and second operations.
 8. The control system of anindustrial truck according to claim 1, wherein said second switchoutputs electric signal corresponding to operational positions of saiddevice.
 9. The control system of an industrial truck according to claim1, wherein said actuator is operated by using the gravitation against amachine element.
 10. The control system of an industrial truck accordingto claim 9, wherein said machine element is one of a crane arm of atruck crane, a shovel of a shovel type excavator, a fork of a forklifttruck, a ladder of a fire-fighting vehicle, a hatch of a refusecollector and a ramp of a car carrier.
 11. A controlling method of anindustrial truck, wherein said industrial truck including: a firstswitch which is provided for a body; a second switch which is providedfor said body; and a hydraulic circuit which is used for operating ofsaid actuator and includes hydraulic fluid, said hydraulic circuitincludes: a control valve which includes a spool (22D, 22N, 22U) thatposition is changed by said operating device, a first circulating linewhich includes said control valve, wherein said hydraulic fluidcirculates through said first circulating line, a hydraulic line whichconnects said spool (22D, 22N, 22U) with said actuator, wherein saidhydraulic fluid passes through said hydraulic line, and a drive lockvalve which is provided for said hydraulic line, said controlling methodcomprising: (a) detecting whether or not an operator sits down on aseat, and carrying out a first operation based on said detection resultby said first switch; (b) detecting whether or not a device foroperating an actuator is operated, and carrying out a second operationbased on said detection result by said second switch; and (c) carryingout blocks said hydraulic line by using said drive lock valve, based onone of said first operation and said first and second operations. 12.The controlling method of an industrial truck according to claim 11,wherein said step (c) includes: (c1) closing said drive lock valve toblock said hydraulic line under a condition that said first switch doesnot carries out said first operation.
 13. The controlling method of anindustrial truck according to claim 11, wherein said first operation isto output a first signal indicating that said operator sits down on theseat, and said second operation is to output a second signal indicatingthat said device for operating an actuator is operated.
 14. Thecontrolling method of an industrial truck according to claim 11, whereinsaid step (a) includes: (a1) detecting a first status that said operatorsits down on the seat; (a2) detecting a second status that said operatordoes not sit down on the seat; and (a3) carrying out said firstoperation when a predetermined time period passes since just after saidfirst situation changes to said second situation.
 15. The controllingmethod of an industrial truck according to claim 11, wherein said firstoperation takes priority of said second operation in said step (c). 16.The controlling method of an industrial truck according to claims 11,wherein said actuator is operated by using the gravitation against amachine element.
 17. The controlling method of an industrial truckaccording to claim 11, wherein said step (b) includes: (b1) detectingwhether or not a device for operating an actuator is operated to apredetermined direction, and (b2) carrying out a second operation whensaid device is operated to said predetermined direction.
 18. Thecontrolling method of an industrial truck according to claim 11, furthercomprising: (d) opening a unloading valve to connect an upstream of saidunloading valve with an hydraulic fluid tank directly, based on one ofsaid first operation and said first and second operations, wherein saidunloading valve is included in a second circulating line, and operatesin response to said first operation, said second circulating line isconnected in parallel with said first circulating line, and does notinclude said control valve, wherein said hydraulic fluid bypasses saidcontrol valve through second circulating line.
 19. The controllingmethod of an industrial truck according to claim 18, wherein said step(d) includes: (d1) opening said unloading valve to connect said upstreamof said unloading valve with said hydraulic fluid tank directly, under acondition that said first switch does not carries out said firstoperation.